Precursors, particularly aminosilane precursors that can be used for the deposition of silicon-containing films, including but not limited to, silicon nitride, silicon oxide, silicon carbo-nitride, and silicon oxynitride films are described herein. In one aspect, described herein is a method for making aminosilane precursors. In yet another aspect, described herein is the use of the aminosilane precursors for depositing silicon-containing dielectric films in the fabrication of integrated circuit devices. In these or other aspects, the aminosilane precursors may be used for a variety of deposition processes, including but not limited to, atomic layer deposition (“ALD”), chemical vapor deposition (“CVD”), plasma enhanced chemical vapor deposition (“PECVD”), low pressure chemical vapor deposition (“LPCVD”), and atmospheric pressure chemical vapor deposition.
Silicon-containing dielectric films play an important role in the fabrication of semiconductor devices or integrated circuits. In the fabrication of semiconductor devices, a thin passive layer of a chemically inert dielectric material such as, for example, silicon nitride may be essential. One or more thin layers of silicon nitride may act within the device as, for example, a diffusion mask or barrier, an oxidation barrier, a gate insulator for trench isolation, a capacitor dielectric, an intermetallic material with high dielectric breakdown voltage, and/or a passivation layer. Silicon nitride film may also be used as sidewall spacers in metal oxide semiconductor alone, or in combination with silicon oxide and/or silicon oxynitride dielectrics in devices such as Groups IV and 11-V transistors. Other applications for silicon-containing dielectrics such as silicon nitride films are found, for example, in the reference Semiconductor and Process Technology Handbook, edited by Gary E. McGuire, Noyes Publication, New Jersey, (1988), pp. 289-301.
Several classes of silicon-containing compounds can be used as precursors for silicon-containing films such as silicon nitride films. Examples of these silicon-containing compounds suitable for use as precursors include silanes, chlorosilanes, polysilazanes, aminosilanes, and azidosilanes. Inert carrier gas or diluents such as, but not limited, helium, hydrogen, nitrogen, etc., are also used.
Low pressure chemical vapor deposition (LPCVD) processes are one of the more widely accepted methods used by semiconductor industry for the deposition of silicon-containing films. Low pressure chemical vapor deposition (LPCVD) using ammonia may require deposition temperatures of greater than 750° C. to obtain reasonable growth rates and uniformities. Higher deposition temperatures are typically employed to provide improved film properties. One of the more common industry methods to grow silicon nitride or other silicon-containing films is through low pressure chemical vapor deposition in a hot wall reactor at temperatures >750° C. using the precursors silane, dichlorosilane, and/or ammonia. However, there are several drawbacks using this method. For example, certain precursors, such as silane and dichlorosilane, are pyrophoric. This may present problems in handling and usage. Also, films deposited from silane and dichlorosilane may contain certain impurities. For example, films deposited using dichlorosilane may contain certain impurities, such as chlorine and ammonium chloride, which are formed as byproducts during the deposition process. Films deposited using silane may contain hydrogen.
Japanese Patent 6-132284 describes the formation of silicon nitride films using organosilanes having a general formula (R1R2N)nSiH4-n by either a plasma enhanced chemical vapor deposition or thermal chemical vapor deposition in the presence of ammonia or nitrogen. These organosilane precursors were tertiary amines and did not contain NH bonding. The deposition experiments were carried out in a single wafer reactor at 400° C. at pressures ranging from 80-100 Torr.
The reference Sorita et al., Mass Spectrometric and Kinetic Study of Low-Pressure Chemical Vapor Deposition of Si3N4 Thin Films From SiH2Cl2 and NH3, J. Electro. Chem. Soc., Vol. 141, No. 12, (1994), pp 3505-3511, describes the deposition of silicon nitride using dichlorosilane and ammonia in a LPCVD process. The major products in this process are aminochlorosilane, silicon nitride and ammonium chloride. As previously mentioned, formation of ammonium chloride may be a major drawback of using Si—Cl containing precursors. The formation of ammonium chloride may lead to, inter alia, particle formation and deposition of ammonium chloride at the back-end of the tube, in the plumbing lines, and the pumping system. Processes which contain chlorine in the precursors may also result in NH4Cl formation. These processes may require frequent cleaning and result in large down time of the reactors.
The reference B. A. Scott et al., Preparation of Silicon Nitride with Good Interface Properties by Homogeneous Chemical Vapour Deposition, Chemtronics, 1989, Vol. 4, Dec., pp. 230-34, describes the deposition of silicon nitride using silane and ammonia by a homogenous CVD process at gas temperatures ranging from 500-800° C. while maintaining the substrate temperature at 200-500° C. As previously mentioned, the use of silane as a precursor may introduce hydrogen impurities into the film.
The reference J. M. Grow et al., Growth Kinetics and Characterization of Low Pressure Chemically Vapor Deposited Si3N4 Films from (C4H9)2SiH2 and NH3, Materials Letters, 23, (1995), pp. 187-193, describes the deposition of silicon nitride using ditertiarybutylsilane and ammonia by a LPCVD process using temperatures ranging from 600-700° C. The deposited silicon nitride films were contaminated with approximately 10 atomic weight percent of carbon impurities.
The reference W-C. Yeh, R. Ishihara, S. Moishita, and M. Matsumura, Japan. J. Appl. Phys., 35, (1996) pp. 1509-1512, describes a low temperature deposition of a silicon-nitrogen film using hexachlorodisilane and hydrazine near 350° C. The films are unstable in air and slowly converted to a silicon-oxygen film.
The reference A. K. Hochberg and D. L. O'Meara, Diethylsilane as a Silicon Source for the Deposition of Silicon Nitride and Silicon Oxynitride Films By LPCVD, Mat. Res. Soc. Symp. Proc,. Vol. 204, (1991), pp. 509-514, discloses the formation of silicon nitride and silicon oxynitride films using diethylsilane with ammonia and nitric oxide by LPCVD. The deposition is carried out in a temperature range of 650° C. to 700° C. The deposition is limited generally to a temperature of 650° C. as the deposition rate drops to below 4 Angstroms/minute at lower temperatures. In the LPCVD process, precursors which contain direct Si—C carbon bonds result in carbon contamination in the films. Carbon free deposition requires greater than 5:1 NH3 to precursor ratios. At lower ammonia concentrations, the films were found to contain carbon. Diethylsilane and ammonia processes typically require covered boats or temperature ramping to improve uniformities across the wafers.
U.S. Pat. No. 5,234,869 (“the '869 patent”) discloses the formation of a silicon nitride film by LPCVD using Si(N(CH3)2)4 and ammonia as reactant gases at 700° C. and a pressure of 0.5 Torr. Other reactants selected from the group consisting of SiH(N(CH3)2)3, SiH2(N(CH3)2)2, and SiH3(N(CH3)2) in combination with ammonia or nitrogen were also suggested as reactants. The '869 patent also discloses decreasing the deposition temperature to 300° C. through the use of a plasma produced from a gas or exciting a gas by radiating it with an ultra-violet beam.
The reference R. G. Gordon and D. M. Hoffman, Silicon Dimethylamido Complexes and Ammonia as Precursors for the Atmospheric Pressure Chemical Vapor Deposition of Silicon Nitride Thin Films, Chem. Mater., Vol. 2, (1990), pp 480-482 disclose other attempts to reduce the amount of carbon in the silicon nitride film involved aminosilanes, such as tetrakis (dimethylamino) silane. The reference discloses the deposition of silicon nitride films via APCVD using the precursor tetrakis(dimethylamido)silane Si(NMe2)4 and ammonia at a deposition temperature range of 600-750° C. The reference also teaches that film depositions using the Si(NMen)4-n without ammonia at a deposition temperature of 750° C. resulted in films that were obtained at slower growth rates and with large amounts of carbon (22-30%) and oxygen (15-17%) contamination.
U.S. Pat. No. 5,874,368 (“the '368 patent”) describes the use of bis(tertiarybutylamino)silane (t-C4H9NH)2SiH2) and ammonia to deposit a silicon nitride film using a LPCVD process at a temperature range of 500° to 800° C.
Precursors that are used in depositing silicon nitride films such as BTBAS and chlorosilanes generally deposit the films at temperatures greater than 550° C. The trend of miniaturization of semiconductor devices and low thermal budget requires lower process temperature and higher deposition rate. The temperature, at which the silicon nitride film is deposited, should decrease in order to prevent ion diffusion in the lattice, particularly for those substrates comprising metallization layers and on many Group III-V and II-VI devices. Presently, none of the currently available silicon nitride precursors are chemically active enough to allow film deposition to occur at temperatures lower than 550° C. via CVD or ALD. Accordingly, there is a need in the art to provide precursors for the deposition of silicon nitride or other silicon-containing films that allow are sufficiently chemically reactive to allow deposition via CVD, ALD or other processes at temperatures of 550° C. or below.